That's an excellent link. I don't have formal training either. I have, however, been influenced by two books. The first, by Robin Williams (not the comedian) is called, "The Non-designers Design Book." I was wowed with her easy to understand explanation of basic design principls. The second is by Stan Lee (the comic book guy) and called "Draw The Marvel Way." He includes sections on composition and how to make it very dynamic. That was an eye opener for me. I'm not always so good at implementing the things they talk about, but now I have a kind of "bar" to work toward. That's a good thing.

Before they made me they broke the mold!
http://home.roadrunner.com/~kflach/